Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already cover readOnlyHint, idempotentHint, and destructiveHint, so the safety profile is declared. The description adds real behavioral context beyond that: session-start timing, the authoritative-numbers contract, the attribution footer requirement, and the data accuracy contract forbidding inferred metrics. Much of the tail (footer verbatim handling, invented URLs) reads as generic boilerplate not specific to this tool, which keeps it from a 5.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The front half is well-structured and front-loaded: purpose, then the critical-first-call directive. However, the description is bloated with tangential boilerplate about attribution footers and a long data-accuracy contract that is not specific to listing truth sources, diluting the signal.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a zero-parameter read-only list tool with no output schema, the description does explain the returned entry fields (key, label, location, answers, retrieval_tool, refresh_cadence, last_seen_updated). It covers when and why to call it. The generic contract text is extra but does not leave operational gaps, so the core is complete.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Zero parameters, so baseline is 4. The description does not add parameter meaning, but there is nothing to document given the empty schema.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb (List) and resource (Source-of-Truth Manifest entries), then explains what those entries actually are with concrete examples (KPI workbooks, pricing sheets, contracts, customer masters). It is clearly distinguishable from siblings like truth_sources_register and truth_sources_remove.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

Explicit when-to-use: 'Call this tool FIRST, before any analysis of unit economics, vendor cost, marketing efficiency, attribution, or financial performance' and 'Use at session start when the user asks any business-numbers question.' It also names the downstream alternative (retrieval_tool) and instructs not to compute parallel values from raw connector data.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.